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Book Review, © Copyright 2001, Jim Loy
This is subtitled, "A Codemaker's war, 1941-1945." Mr. Marks made ciphers to replace the poem cipher that was killing so many spies and saboteurs in German-occupied countries. Read of the wonderful people who parachuted into enemy territory, only to send a few messages, get captured, be tortured, and then be shot. Read of the young women (FANYs) who decrypted their messages, sometimes after thousands of attempts when a typographical error garbled the message. Read about the ugly power struggle among rival British covert operations and code departments. Read about the mysterious Herr Giskes who is busy killing agents and then pretending to be those agents. And read about the agent who could never tell a lie. Mr. Marks was an oddball, a black sheep, and a super codemaker and codebreaker. He secretly and openly rebelled against the bureaucracy, the chain of command, and the waste of life. He takes no one seriously, especially himself, except the Germans, the agents in the field, and the FANYs. And under one photograph, we find that Mr. Marks later restored the reputation of one of the agents who had been accused of collaborating with the Germans.
This is a really good story.
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Double transposition poem cipher: As far as I remember, this book does not adequately explain the double transposition poem cipher, which killed so many agents, and plays an immense roll in the book. Here are some details.
Let's say that you have a key: THISISMYKEY, and a message:
TWAS THE NIGHT BEFORE CHRISTMAS AND ALL THROUGH THE HOUSE NOT A CREATURE WAS STIRRING NOT EVEN A MOUSE
Now we number the letters of the key in alphabetical order:
T H I S I S M Y K E Y 9 2 3 7 4 8 6 10 5 1 11
Then we write the message under this numbered key:
T H I S I S M Y K E Y 9 2 3 7 4 8 6 10 5 1 11 T W A S T H E N I G H T B E F O R E C H R I S T M A S A N D A L L T H R O U G H T H E H O U S E N O T A C R E A T U R E W A S S T I R R I N G N O T E V E N A M O U S E X X X X
I've added a few X's at the bottom, to make each column of equal length. Then we write down horizontally the column labeled 1 (GRLERTVX) followed by the column labeled 2 (WBTHUTRA), etc., with a blank after each five letters:
GRLER TVXWB THUTR AAEMR SUIMT OSUNE GUIHA HCSEX EENHT AOESF AOERN OHRAG OWNST TSTOA RNNCD TASTX HILHE IEXXX
This was one transposition. In reality, because this was a double transposition cipher, we do it all again with a different key. The key would actually be taken from the agent's favorite poem, which the codebreakers in London had a copy of. I used X's to fill out the message. Something more clever was done, in reality. And extra characters were added at preplanned places in the message, to demonstrate that the sender is who he/she is supposed to be. Anyway, knowing the key, the recipients of this message can easily decrypt it and read it.
The above encrypted message is a huge anagram of the original message. Without the key, it would seem to be nearly impossible to break. But, in a military message, there would be key words (ENDOFMESSAGE), the names of people and places, and numbers spelled out. Also, the Germans may guess which poem is your favorite. It turns out that after a few minutes, most of these messages could be broken.